[Rd] Problems with plot and Quartz device / What is alpha?

[Thomas Richardson]

PS Please forgive my ignorance, but when you say:


> BTW: you may want to use something like pch=19, cex=0.1 (and maybe add some 
> alpha to get a quick density estimation).

I don't know what alpha refers to here.

Thanks again.

Best wishes,

Thomas

>
> Cheers,
> S
>
>
>> So I guess it might be related to the
>> "special treatment" of "." described on help(points) ??
>> ---
>> Value pch="." (equivalently pch = 46) is handled specially. It is a 
>> rectangle of
>> side 0.01 inch (scaled by cex).
>> ---
>> 
>> I find this behaviour unnerving: the (resized) plots made it look as if 
>> there
>> was a lot of structure in the data, but on closer inspection it turned out 
>> to be
>> entirely a consequence of the quartz device and plot function!
>> 
>> I can't imagine that this behaviour is intended - even if it were intended 
>> to
>> suppress points (like some axis labels) - it seems strange that enlarging 
>> the
>> window makes points disappear. (I also tried setting dpi=72 in quartz(), 
>> but
>> this did not fix the problem).
>> 
>> Thanks in advance.
>> 
>> Thomas
>> 
>> ------------------------------------------------------
>> sessionInfo()
>> R version 2.9.0 (2009-04-17)
>> i386-apple-darwin8.11.1
>> 
>> locale:
>> en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
>> 
>> attached base packages:
>> [1] stats     graphics  grDevices utils     datasets  methods   base
>> 
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>> 
>> 
>